1. Field of the Invention
The present invention relates to a liquid discharge head for discharging a desired liquid by generation of bubbles formed by applying thermal energy to the liquid, and a head cartridge and a liquid discharge apparatus that employ such a liquid discharge head. In particular, the present invention relates to a liquid discharge head comprising a movable member that is displaced (moved) by utilizing bubble generation, a head cartridge and a liquid discharge apparatus employing such a liquid discharge head.
In addition, the present invention can be applied for an apparatus such as a printer that performs recording on a recording medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood or ceramics, a copy machine, a facsimile machine that has a communication system, and a word processor having a printing unit and for an industrial recording apparatus compositely combined with various processing apparatuses.
The "recording" in this invention involves not only the transfer of a meaningful image, such as a character or a graphic figure, to a recording medium, but also the transfer of a meaningless image, such as a pattern.
2. Related Background Art
The ink-jet recording method is well known as the so-called bubble-jet recording method which comprises applying thermal energy to ink, to generate a conditional change in the ink, which is accompanied by a drastic volume change (the generation of bubbles), discharging the ink through a discharge opening, by the energy generated due to the conditional change, and landing the ink on the surface of a recording medium to form an image. As is disclosed in U.S. Pat. No. 4,723,129, a recording apparatus employing the bubble-jet recording method generally comprises a discharge opening through which ink is discharged, an ink flow path that communicates with the discharge opening, and an electro-thermal converting member that serves as energy generation means for discharging the ink in the ink flow path.
By employing this recording method, an image having a high quality can be recorded rapidly, with reduced noise, and in a head for discharging ink discharge openings can be arranged at a high density.
For these reasons, this recording method has proven to be superior, in that when it is employed, high resolution images, and even color images can be easily produced by compact devices. As a result, the bubble-jet recording method has recently come to be employed in various types of office equipment, such as printers, copy machines and facsimile machines, and also in industrial system equipment, such as textile printing machines.
As the bubble-jet technique has come to be used for products in a number of different fields, there has been an increase in various demands such as the following.
As an example, there is the demand that energy efficiency be enhanced, and the demand is solved by the optimization of the function of a heat generating member i.e., the adjustment of the thickness of a protective film, that effectively improves the efficiency for the transmission of generated heat to liquid.
In addition, to acquire high quality images, proposed are driving conditions that will provide a liquid discharge method, based on the stable generation of bubbles, whereby ink can be preferably discharged at a high speed. Further, from a viewpoint of high rapid recording, proposed are liquid discharge heads having improved flow path shapes that will provide for the high speed refilling of flow paths after the discharge of liquid.
Of such flow paths, the flow path structure shown in FIGS. 42A and 42B is described in Japanese Patent Application Laid-open No. 63-199972. The flow path structure and the head manufacturing method, which are described in this application, are provided by focusing on a backflow wave that occurs in association with the generation of bubbles (the pressure directed in a direction opposite to the direction of a discharge opening, i.e., pressure applied in the direction of a liquid chamber 1012). The energy used to produce this backflow wave is considered to be a lost energy, since the energy is not directed, in the discharge direction.
The invention shown in FIGS. 42A and 42B discloses a valve 1010, which is separated from a bubble-generating region that is defined by a heat-generating member 1002, and which is positioned opposite to a discharge opening 1011 with the heat-generating member 1002 positioned between them.
In FIG. 42B, the valve 1010 is initially positioned such that it is attached to the ceiling of a flow path 1003, and it is bent down into the flow path 1003 when bubbles are generated. This invention discloses that the backflow wave is partially controlled by the valve 1010 to restrict energy loss.
However, as is apparent in the above arrangement, when bubbles are generated in the flow path 1003 for holding liquid to be discharged, the partial restriction of a backflow wave by the valve 1010 is not practical in the discharge of the liquid.
The backflow wave is not directly related to the discharge of the liquid. When the backflow wave occurs in the flow path 1003, as is shown in FIG. 42A, the bubble pressure that directly affects the discharge has already enabled the liquid to be discharged from the flow path 1003. Therefore, apparently, even when a part of the backflow wave is restricted, this has not great effect on the discharge of the liquid.
In the above conventional liquid discharge head, however, since heating is repeated while the heat-generating member is in contact with ink, precipitate due to ink scorching is deposited on the surface of the heat-generating member. Depending on the ink type, more precipitate is generated and deposited, which can result in unstable bubble generation and make the preferable discharge of ink difficult. In particular, since driving frequencies have been increased in accordance with recent requests that recording speeds be further increased, multiple discharge openings have been provided and print heads have been elongated, it is difficult to smoothly, uniformly and stably effect the rapid refilling of a flow path with ink in the direction of a discharge opening. As a result, the recording quality has also been deteriorated.
In addition, preferable ink discharge is difficult when a liquid to be discharged is easily deteriorated by heat or when sufficient bubbles can not be generated in a liquid to be discharged.